1 /* $NetBSD: freopen.c,v 1.22 2018/01/17 01:24:30 kamil Exp $ */
2
3 /*-
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include <sys/cdefs.h>
36 #if defined(LIBC_SCCS) && !defined(lint)
37 #if 0
38 static char sccsid[] = "@(#)freopen.c 8.1 (Berkeley) 6/4/93";
39 #else
40 __RCSID("$NetBSD: freopen.c,v 1.22 2018/01/17 01:24:30 kamil Exp $");
41 #endif
42 #endif /* LIBC_SCCS and not lint */
43
44 #include <sys/types.h>
45 #include <sys/stat.h>
46
47 #include <assert.h>
48 #include <errno.h>
49 #include <fcntl.h>
50 #include <unistd.h>
51 #include <stdio.h>
52 #include <stdlib.h>
53 #include <wchar.h>
54 #include <limits.h>
55 #include "reentrant.h"
56 #include "local.h"
57
58 /*
59 * Re-direct an existing, open (probably) file to some other file.
60 * ANSI is written such that the original file gets closed if at
61 * all possible, no matter what.
62 */
63 FILE *
freopen(const char * file,const char * mode,FILE * fp)64 freopen(const char *file, const char *mode, FILE *fp)
65 {
66 int f;
67 int flags, isopen, oflags, sverrno, wantfd;
68
69 _DIAGASSERT(file != NULL);
70 _DIAGASSERT(mode != NULL);
71 _DIAGASSERT(fp != NULL);
72
73 if ((flags = __sflags(mode, &oflags)) == 0) {
74 (void) fclose(fp);
75 return NULL;
76 }
77
78 if (!__sdidinit)
79 __sinit();
80
81 /*
82 * There are actually programs that depend on being able to "freopen"
83 * descriptors that weren't originally open. Keep this from breaking.
84 * Remember whether the stream was open to begin with, and which file
85 * descriptor (if any) was associated with it. If it was attached to
86 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
87 * should work. This is unnecessary if it was not a Unix file.
88 */
89 if (fp->_flags == 0) {
90 fp->_flags = __SEOF; /* hold on to it */
91 isopen = 0;
92 wantfd = -1;
93 } else {
94 /* flush the stream; ANSI doesn't require this. */
95 if (fp->_flags & __SWR)
96 (void)__sflush(fp);
97 /* if close is NULL, closing is a no-op, hence pointless */
98 isopen = fp->_close != NULL;
99 if ((wantfd = __sfileno(fp)) == -1 && isopen) {
100 (void) (*fp->_close)(fp->_cookie);
101 isopen = 0;
102 }
103 }
104
105 /* Get a new descriptor to refer to the new file. */
106 f = open(file, oflags, DEFFILEMODE);
107 if (f < 0 && isopen) {
108 /* If out of fd's close the old one and try again. */
109 if (errno == ENFILE || errno == EMFILE) {
110 (void) (*fp->_close)(fp->_cookie);
111 isopen = 0;
112 f = open(file, oflags, DEFFILEMODE);
113 }
114 }
115 sverrno = errno;
116
117 /*
118 * Finish closing fp. Even if the open succeeded above, we cannot
119 * keep fp->_base: it may be the wrong size. This loses the effect
120 * of any setbuffer calls, but stdio has always done this before.
121 */
122 if (isopen && f != wantfd)
123 (void) (*fp->_close)(fp->_cookie);
124 if (fp->_flags & __SMBF)
125 free((char *)fp->_bf._base);
126 fp->_w = 0;
127 fp->_r = 0;
128 fp->_p = NULL;
129 fp->_bf._base = NULL;
130 fp->_bf._size = 0;
131 fp->_lbfsize = 0;
132 if (HASUB(fp))
133 FREEUB(fp);
134 WCIO_FREE(fp);
135 _UB(fp)._size = 0;
136 FREELB(fp);
137
138 if (f < 0) { /* did not get it after all */
139 fp->_flags = 0; /* set it free */
140 errno = sverrno; /* restore in case _close clobbered */
141 return NULL;
142 }
143
144 /*
145 * If reopening something that was open before on a real file, try
146 * to maintain the descriptor. Various C library routines (perror)
147 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
148 */
149 if (wantfd >= 0 && f != wantfd) {
150 if (dup2(f, wantfd) >= 0) {
151 (void) close(f);
152 f = wantfd;
153 }
154 }
155
156 /*
157 * File descriptors are a full int, but _file is only a short.
158 * If we get a valid file descriptor that is greater or equal to
159 * USHRT_MAX, then the fd will get sign-extended into an
160 * invalid file descriptor. Handle this case by failing the
161 * open. (We treat the short as unsigned, and special-case -1).
162 */
163 if (f >= USHRT_MAX) {
164 (void)close(f);
165 errno = EMFILE;
166 return NULL;
167 }
168
169 fp->_flags = flags;
170 fp->_file = f;
171 fp->_cookie = fp;
172 fp->_read = __sread;
173 fp->_write = __swrite;
174 fp->_seek = __sseek;
175 fp->_close = __sclose;
176
177 /*
178 * When reopening in append mode, even though we use O_APPEND,
179 * we need to seek to the end so that ftell() gets the right
180 * answer. If the user then alters the seek pointer, or
181 * the file extends, this will fail, but there is not much
182 * we can do about this. (We could set __SAPP and check in
183 * fseek and ftell.)
184 */
185 if (oflags & O_APPEND)
186 (void) __sseek((void *)fp, (off_t)0, SEEK_END);
187 return fp;
188 }
189